Problem: William has taken 4 tests and his average score so far is 88. If he gets 100, a perfect score, on the remaining 2 tests, what will his new average be?
Answer: If he gets 100 on the remaining tests, the sum of his scores will be $4 \cdot 88 + 2 \cdot 100 = 552$ His overall average will then be $552 \div 6 = 92$.